I do realize that. The war in Ukraine is not being supported by Nato. They are sending supplies but the alliance is not entering Ukraine against Russia so as to not create a wider conflict. Note that Ukraine is not a NATO signatory while Canada is.
In the case of the US annexing Canada,the strategic analysis would give two options. Either immediately oppose US aggression and form a bloc independent of them, or tacitly approve of it and leave yourself open to the same thing happening to you and your neighbours.
Sending munitions/equipment to one side means that you support that side ;)
I do not know what kind of mental gymnastics you make when you say NATO doesn't support the war in Ukraine, but it actually does - with the NATO SG going to Ukraine in a show of support.
AFAIK, there is no precedent to what will happen if a NATO country attacks another NATO country - we came close to that when the Turks and the Greeks almost started fighting a few years back.
Directly support as the commenter I was replying to was implying. Europe is not barely holding back Russia. Ukraine is. Article 5 would be invoked and the NATO states would decide what support to send. Greece and Turkey fighting over some islands isn't the same as the strongest nation in the world annexing its neighbours. There would be broad public support in Europe to oppose the U.S. simply on principle, let alone the security concerns.
